(WASHINGTON, Reuters)The risk of a heart attack jumps nearly fivefold during the first hour after smoking marijuana.
（路透社华盛顿电）开始抽大麻的一个小时之内，心脏病发作的危险性几乎会激增五倍。

this poses a particular threat to middle-aged users of the drug, especially those over age 45.
这种危险性对于中年的大麻吸食者特别严重，尤其是超过四十五岁的人。
The increased risk from marijuana was more dangerous than sexual intercourse for a sedentary person.
对于久坐的人而言，抽大麻所增加的危险性比性行为还高。
Marijuana can cause the heart rate to double.
大麻会让心跳速度增快一倍。